Longstanding readers of these columns may remember a certain 10.8V jigsaw (sorry Bosch, I "forgot" your magic 1.2V!). The (red) blade clamp on the end of the piston (Bosch-speak: "lifting rod") wasn't fitted such that it held the blade true...


I've been preoccupied recently with the after effects of a physically small but consequentially huge operation (and it's been jolly not-comfy, to boot). My brain slows down under such circumstances. The after effects have been easing off, and I'm finding I can do more as each day passes. First physio appointment tomorrow morning. But I digress.
I was mentally kicking myself over the jigsaw as it was down to me not spotting the problem in warranty. The penny dropped at the back end of last week that the whole piston might be available as a spare part, and possibly affordable (or at least cheaper than another entire jigsaw!).
So I Googled it halfheartedly: Yes it was available! Bad news: the part ranged from 50 to 90 UKP depending on the parts supplier (wow!). Then I discovered the Robert Bosch trade spares site.
The same part number seemed to be used on three or four 10.8V models, and _much_ cheaper: 36.16 UKP (including VAT and 4.20 delivery).
It had to be worth a punt.
It arrived yesterday. First obvious difference is that the original blade clamp was red plastic; the replacement is black.


Second, not-so-obvious thing is that the replacement has a bit of plastic sticking out at the back, and, once fitted, it fouls the case of the machine and the rear blade support roller mech. This isn't a terribly good pic, but you can probably see the old red one has a slightly different shape, especially nearest the tabletop in the picture.
At a guess the independent spares places have NOS that does fit properly and are simply charging 'because-we-can' prices.
I strongly suspect mine was part of a bad batch in manufacturing that didn't get QC'd and escaped. It _is_ the correct part number, but someone at Bosch updated the design without actually checking the new part fitted. In these days of 3D printing, that's "rather" poor.
Well, I am a man with a Proxxon mini-drill (the gentleman's Dremel!). After I've been beaten up by the physio tomorrow I shall attempt to do battle with back of the black clamp, and we'll see who wins.
I have high hopes of a cheap-ish fix to an annoying problem. Better pictures to follow also as I'll have to strip it down again and re- re-grease it <grrr>.
If anyone cares all these 10.8V Bosch tools seem to be held together with T10 Torx self tappers (for plastic) and a single clip on the back of the battery compartment (slides out and off with a flat-bladed screwdriver). It's a manual job, as they're buried slightly too deep for my cordless set to reach.
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Saturday
It was perishing in the workshop, as I wasn't really moving about enough to get warm. It was, however the nicest place to quickly set up for photography, and it meant I could reassemble the saw without getting SKF's best general purpose grease all over the kitchen table.
Before doing that I had a moment of repair insecurity: I realised the red (old and twisted) piston was pretty sawdust-caked. What if that was upsetting the blade clamp? A bit of poking around inside the clamp with a bit of copper wire did produce a lot of crud. The blade seemed to fit better, but still on a squint, or so it seemed. I thought I should do a side-by-side comparison, which turned out to be a bit tricky to photograph:

[click on the image for a bigger version]
The 'Spam key" end of the thing is held down to the bench with a weight, such that the wings of the key are parallel with the benchtop (in the important axis), and the paintbrush handle is merely a prop for the back of the blade in each case.
If you look
really hard you can see the blade held in the red clamp isn't straight, it's twisted in the direction of the white arrow. It's not by much, but it's quite enough such that you can't run the jigsaw against a straight edge, as it won't cut straight. It will either bind up or dive away depending which side the guide is on.
The last two pics are looking end on into the two clamps. Ignore the stainless cover plate. The black clamp mech has a slot that's at a true
(-ish) right angle to the 'key' part, as it should be. The red one is indeed twisted (sorry - I left a blade in it - was shivering by that point!).


To be clear, the red/black plastic bit is a locking ring/blade release, which rotates by a bit less than a quarter turn. The slot the blade sits in doesn't rotate and should be perpendicular to the wings of the 'key' part.
So it's now reassembled, with the black, replacement clamp fitted. No fettling was needed, but loadsa grease added to anything remotely greaseworthy in the mechanism. Testing with a few batteries showed it's running true, with a satisfying run-on (thanks to the extra grease).
And that one's now done - total cost 35 UKP (would've been zero in warranty). Phew.
Bosch owes me really, but it's a handy little thing for small jobs, and nice to have it trustworthy at last.
PS: A caution to anyone with the same problem: you really can't repair these things. the main "shaft" of the thing is actually a tube, and must have a spring inside to eject blades. It's crudely pressed or stamped onto the 'key' part. It's not impossible, I guess, to cut it off then braze it back straight, but if I tried it would be melted plastic bits and a spring somewhere in orbit.
The part number is:
2.600.780.190 and it's apparently used on a number of small Bosch jigsaws.